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Avian influenza (or bird flu) is a disease of birds caused by infection with avian influenza type A viruses. These viruses occur naturally among wild aquatic birds worldwide and can infect domestic poultry and other bird and animal species.

Domestic poultry may be infected with highly pathogenic or low pathogenic avian influenza A viruses:

  • The highly pathogenic viruses spread quickly and may kill nearly an entire poultry flock within 48 hours.
  • The low pathogenic viruses may not cause symptoms or may cause only mild symptoms such as ruffled feathers or a drop in egg production.

Public health and poultry scientists are concerned about avian influenza A viruses for several reasons, including:

  1. They threaten domestic poultry throughout the world.
  2. Some viruses have passed sporadically from poultry to humans and caused serious illness and death.
  3. They may change into a form that is highly infectious in humans and spreads easily from person to person.

Avian Influenza and Workers

Avian influenza A viruses usually do not infect humans; however, sporadic cases have been reported. These infections have resulted in a wide range of illnesses from conjunctivitis to mild respiratory symptoms, to fatal pneumonia. The disease can be transmitted to unprotected workers who have contact with infected wild birds, poultry, or contaminated surfaces.

Examples of poultry workers and other workers at risk include the following:

  • Broiler breeder farms, hatcheries, grow-out farms, and processing plant workers
  • Layer farm workers
  • Disease control and eradication workers (including Federal, contract, and company workers)
  • Live-bird market workers
  • Wildlife biologists who handle birds

waterfowl duck img1 img3

Photos courtesy of U. S. Department of Agriculture

Avian influenza A viruses are excreted in the droppings, saliva, and nasal secretions of infected birds. Human infection may occur when avian influenza A viruses infect humans through the mouth, nose, eyes, or lungs. Scientists believe that the virus may be transmitted to humans from contact with one of the following:

  • Infected wild birds or poultry that are sick or dead
  • Droppings of infected birds
  • Contaminated litter
  • Contaminated surfaces such as egg collection containers

Although the human health risk of exposure to low pathogenic avian influenza A viruses is not known, protective measures should be taken for anyone likely to have exposure to either low pathogenic or highly pathogenic avian influenza A viruses in an enclosed setting.

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  • Page last reviewed: June 29, 2015
  • Page last updated: June 29, 2015 The U.S. Government's Official Web PortalDepartment of Health and Human Services
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